An 8-year-old Bronx boy today slashed a classmate across the neck with a double-edged razor — at a school that’s already canceled graduation once because of out-of-control behavior, cops and parents said.

Police sources said the pint-sized perp told cops he brings the blade to school with him every day because some of the kids don’t like him, ABC-TV reported.

The boy snapped on the playground during lunch after feuding with his 9-year-old victim at the violence-plagued school — PS 132 in the Morrisania section — on and off for the past few days, a law-enforcement source told The Post.

The victim had yelled, “B—-!” at the boy just before he was cut, sources told ABC.

The stunned 9-year-old was sliced on the back of his neck — a “deep laceration’’ just inches from an artery — shortly before noon, sources said.

He was rushed to Bronx Lebanon Hospital fewer than three blocks away, where he was received stitches and was listed in serious but stable condition.

His young attacker was nabbed in the courtyard with the razor still on him, sources said. He was bleeding, too — from a cut he got on his hand while wielding the weapon, they said.

He hauled off to the 42nd Precinct, where he was charged with assault and criminal possession of a weapon, police said.

A source said he could be sent to a juvenile facility while awaiting a hearing in family court.

While shocking, such violence is nothing new at the school, which was temporarily forced to cancel graduation at one point this year, parents said.

The school’s fed-up principal recently “made the announcement that the fifth graders wouldn’t be having graduation because of their behavior,’’ said Gwendolyn Primus, whose 10-year-old grandson is in fourth grade at the school, which is K-5.

“When parents protested and the community went into an uproar … she said she’ll have a ‘moving up’ ceremony that will take place in the auditorium’’ instead of the usual, more fancy graduation spot at Hostos College.

City Education Department spokeswoman Margie Feinberg said, “The graduation has not been cancelled. The principal said there will be a low-key event at the school.’’

A woman with several children at the school said the problem won’t go away with a slap on the wrist.

“Every time you turn around, there’s something going on in that school,’’ she said, adding that staffers told her of a fifth-grade girl who had threatened to “bring in a knife and kill somebody” — not once but three times.

“Kids have been threatened, kids have been hurt,” said the woman, who did not want to be identified.

“You got a little boy now that almost lost his life in there because y’all don’t take things serious when kids make these threats.”

The school got an overall “C’’ rating from parents, teachers and students last year for its school environment — or a measly 4.2 out of 15 points.

Its student performance on state testing was even more dismal, rating a “D.”

In 2010, a then-10-year-old female student was led of the school in handcuffs after a particularly nasty fight, and she sued the NYPD for it.